Process of preparing transparentized double face photoprinting material for the so-called dry process



1968 A J. P. VAN GROENLAND PROCESS OF PREPARING TRANSPARENTIZED DOUBLE FACE PHOTOPRINTILNG MATERIAL FOR THE SO-CALLEI.) DRY PROCESS Filed NOV. 13, 1965 GAS PERMEABILITY GAS PERMEABILITY ACCORDING TO BEKK. TRANSEXPOSURE TIME I SECONDS CONCENTRATION TRAN SPARENTIZING AGENT INVENTOR.

wmwmww United States Patent PROCESS OF PREPARING TRANSPARENTIZED DOUBLE FACE PHOTOPRINTING MATERIAL FOR THE SO-CALLED DRY PROCESS Adrianus Johannes Petrus van Groenland, Delft, Netherlands, assignor to N.V. Lichtdrukpapierfabriek De Atlas, Delft, Netherlands Filed Nov. 13, 1963, Ser. No. 323,477 Claims priority, application Netherlands, Nov. 15, 1962, 285,544 4 Claims. (Cl. 9675) ABSTRACT OF THE DISCLOSURE Transparentized photoprint paper provided on each side with a photosensitive coating and having a gas permeability (measured with the Bekk apparatus) of below 50 seconds is provided. There is provided the process for preparing such photoprint paper involving the improvement according to which the material is incompletely transparentized by means of a transparentizing agent which keeps the gas permeability of the resultant transparentized product, measured with the Bekk apparatus, at below 50 seconds. The invention also provides a papertransparentizing composition for use in the preparation of such photoprint paper.

According to the prevailing photoprinting methods, it is possible to make from transparent or translucent originals, in addition to the normal prints on paper, also special prints, which, in their turn, can be used as originals for further copying. In connection with the re-printing of this special copy (hereinafter called intermediate tracing), it is desirable for the carrier material of the intermediate tracing to have a perviousness to light (transparency) as great as possible.

It is also necessary for the colour of the lines and the text carried by the intermediate tracing to have the highest possible absorption value in respect of the light which is active in the photoprinting process, namely, ultraviolet and violet light. For a good U.V. density, preferably a yellow or yellow-containing colour is applied.

Furthermore, a good, sharp print requires the UV.- opaque line to be in contact as closely as possible with the material to be exposed; for this reason the intermediate tracing is exposed in mirror-image relationship. Then, however, in order to read the text easily, it must be possible to see through the carrier material from the back.

It is exactly this reading through the material which becomes very ditlicult when a yellow colour is selected which has a good U.V. density. Therefore a brown or greenish line colour is applied, or the material used for the intermediate tracing is photosensitive on both sides: it is then possible to read easily from the back, especially when that side has a brown or blue line colour.

Naturally the readability through the carrier material is not a problem in the case of transparent films (for example, cellulose acetate), or in the case of very transparent paper (transparent drawing paper). However, these materials are not only expensive, but their mechanical characteristics are often unfavourable (they are easi y torn, cannot be folded, tend to curl); a further problem is that for some purposes the material must be suitable to write on.

Mostly, therefore, normal types of paper are used as carrier, in a quality of -8O g./m. free of filling materials. For the sake of the readability, they are rendered photosensitive on both sides, and the UV. opaque side is exposed through the original in mirror-image relation- 3,370,949 Patented Feb. 27, 1968 ship. The photosensitivity of the back is such that the latter can be exposed simultaneously with the front.

A practical requirement in this connection is that it must also be possible for the paper thus exposed to be developed at one time in a developing machine, which is often coupled to the exposure apparatus. This involves that the developing medium should either be admitted to both sides of the material, or must be capable of reaching the back through the material from the front.

Developing machines operating according to the wet or semi-wet process generally moisten (i.e. develop) the material on both sides. Dry process developing machines, however, predominantly admit the developing medium (gaseous ammonia) to one side only.

For this reason, in the case of the dry process, the material which is sensitive on both sides must allow the gas (ammonia) to pass through it to a sufficient extent, in other words, the carrier must be, and, remain, sutficiently porous for the development to be effected at one time.

As a consequence, an important group of carriers, which otherwise satisfy the demands very well, namely, the transparentized papers, cannot just be applied.

By transparentized paper is designated a normal type of paper, suitable for making an intermediate tracing, which has been impregnated with a suitable transparentizing agent, a resin or oil, which has filled the pores of the paper. Normally, these pores contain air; the refraction and reflection of light which is effected on the boundary faces paper-fibre-air are one cause of the non-transparency of normal paper. If the pores are filled with a transparentizing agent, the transparency of the paper is considerably increased, and hence the time required to expose a certain photoprinting material through such paper to a specific degree is decreased correspondingly. This time will hereinafter be referred to as the transexposure time.

This is illustrated in the following Table I.

TABLE I Trans- No. Type of paper exposure 'me, seconds Normal paper, 60 g./m. 54 Paper as 1, now transparentize 33 Normal paper, 45 g./m. 49 Paper as 3, now transparentized 29 Exposed without paper 18 Whereas the transparency is considerably increased (in fact, with the same source of light and employing paper of 45 g./m. it is possible to work 49/29=1.7 times as rapidly), it also appears that the transparentizing agent fills and clogs the pores of the paper to such an extent that the passage of gas is permitted less readily. The results of measurements of the time required for equal For determining this gas permeability or porosity, use has been made of the Bekk apparatus (cf. J. Bekk: Drucktechnische Papierprtifmethoden, Zeitschrift fiir Deutschland Buchdrucker und verwandte Gewerbe 42, 755 (1930); J. Bekk: Drucktechnische Papierpriifung, Der Papierfabrikant, Heft 16 1935, page 137).

It has been found in practice that paper having a gas permeability of more than 50 seconds is no longer suitable as a carrier for photoprinting material which is photosensitive on both sides, if it is desired to develop the latter according to the dry process in one pass. This restriction excludes the commercial transparentized papers:

TABLE III Trans- No. Type of transparentized paper exposure Gas tim permeability seconds 1 -c Amara 402 LT. brown diazotype 43 Impermeablo mat. photosensitive on one 200 side (single face). seconds). Amara 102 l'l'F ditto but black 38 Do.

line A. Ant are 522 I.I. brown blue 38 Do.

double face must be developed twice. 4 Dietzgen 244 (single face brown)" 32 Do. 5 Dietzgen 244 X1 (single face 44 Do.

brown). Ozavcl (single taco brown) 40 Do. Azon Corp. (single face brown) 44 Do. 009 (double i'ace brown, semi- 43 79 seconds.

wet development).

It has now been found that normal paper can be so treated with transparentizing agents that development through the paper is still satisfactorily possible. For it has surprisingly appeared that upon continued transparentization the transparency of the paper increases primarily much more rapidly than could be expected on the ground of the decrease in the gas permeability.

The invention accordingly relates to a process for preparing transparentized photoprinting material which is on both sides provided with a photosensitive coating containing a photosensitive diazo compound together with a coupling component, and which process is characterized by the feature that the material is incompletely transparentized either before or after it has been rendered photosensitive, and this is such a manner that the gas permability of the resultant transparentized product, measured with the Bekk apparatus, remains below 50 seconds.

It turns out, for example, that upon transparentization to a gas permeability of 40 seconds, the transexposure time has already decreased from 49 to 33 seconds, while at best a value of 29 seconds can be attained, i.e.,

of the value which can at best be attained.

This applies to 45 g./n1. paper. For various papers is found, for example.

TABLE IV Normal Best pos- Limit value Paper, gJm. transsible transtransexposure Percentage exposure exposure time, seconds time, seconds time, seconds It is apparent from this table that this method of transparentization is also advantageous in the case of heavier papers, although the user will in practice invariably select qualities between 30 g./m. (with a View to the mechanical strength) and 80 g./m. (in connection with the practically acceptable maximum transexposure time).

Moreover, the additional step of transparentization will only be applied if a reasonable gain in transexposure time can be obtained by complete transparentization on the one hand, while on the other hand the incomplete transparentization according to the invention should result in at least 50% of the maximum transparency that can be attained.

The chemical composition of the transparentizing agent is immaterial. As will appear from the examples, it is always possihle to select a composition which results in a good gas permeability. The transexposure time associated with such gas permeability is substantially constant.

The measured results are independent of the photoprinting characteristics of the material as such. Accordingly, corresponding results are found with blank paper and paper rendered photosensitive, irrespective, also, of whether the transparentization is eiiected before or after the sensitization.

Example 1 Composition 1 2 3 4 Xylene in which dissolved 50% of polystyrene O 5 Kerosene 100 95 90 85 80 75 Of the treated papers, the gas permeability is measured by means of the Bekk apparatus. Also measured is the time required to expose photoprinting paper to the same degree through the test papers under otherwise equal conditions. The measured values result in the curves illustrated in the drawing.

According to the drawing, paper treated with the composition: 14 parts by Weight of the polystyrene solution and 86 parts by weight of kerosene, is still suitable for the purpose, which, indeed, corresponds with the actual test. For practical purposes, a smaller amount of resin will mostly be sufiicient. Thus, a mixture of 12.5 parts by weight of the polystyrene solution and 87.5 parts by weight of kerosene turns out to be very suitable for large-scale production.

Example 2 A base paper as in Example 1, in a quality of 60 g./ 111. is treated in accordance with Example 1. It appears diagrammatically that the compositions: 12.5 parts by weight of the polystyrene solution and 87.5 parts by Weight of kerosene may be expected to produce good results.

This is confirmed by the actual test.

Example 3 Base paper as in Example 2 is transparentized by means of the commerical C.T.S. transparentizing agent; the agent is made up with carbon tetrachloride to the desired concentration for the purpose.

A practicable comprise between the gas permeability and the transparency is attained with parts by weight of C.T.S. agent and parts by weight of carbon tetrachloride.

The C.T.S. agent is prepared by C.T.S. Philadelphia in accordance with US. Patent No. 2,616,815.

Example 4 The paper obtained in the manner mentioned in Examples 1 and 2 is rendered photosensitive on one side according to Recipe (a) and on the other side according to Recipe (b).

A ter exposure and one development in ammonia vapour on one side, there are obtained a brown line with a very good U.V. density on one side and a clearly readable -blue line on the other side.

2,3-di-hydroxynaphthalene-sulphonic acid-6 g 6 Diazo compound (1 NN dimethylaminobenzenediazoniumchloride-4 zinc-chloride double salt) g 0.6 Polyvinyl acetate dispersion cc 5 Isopropanol cc 5 Make up with water to cc 100 Example 5 Base paper as in Examples 1 and 2 is rendered photosensitive by means of the recipes given in Example 4, and transparentized in accordance with Examples 1 and 2.

After exposure and one single-face development in ammonia vapour, there are obtained a brown line With a very good U.V. density on one side and a clearly readable blue line on the other side.

I claim:

1. In a process for preparing transparentized photoprinting material which is on both sides provided with a photosensitive coating containing a photosensitive diazo compound together with a coupling component, the improvement according to which the material is incompletely transparentized by means of a smaller amount of a transparentizing agent than is necessary to completely transparentize, the material being characterized by having a gas permeability, measured with the Bekk apparatus, of below 50 seconds. i

2. A process according to claim 1, wherein the transparentizing is effected with, as transparentizing liquid, a mixture of 10.0-14.0 parts by weight of a 50% solution of polystyrene in xylene and 90.0-86.0 parts by weight of kerosene.

3. A process according to claim 1, wherein the transparentizing is carried out prior to rendering the said coating photosensitive.

4. A process according to claim 1, wherein the transparentizing is carried out after rendering the said coating photosensitve.

References Cited UNITED STATES PATENTS 2,087,609 7/ 1937 Richter 81l9 2,181,160 11/1939 Shankweiler 117 -153 2,501,874 3/1950 Peterson 96-75 X 2,616,815 11/1952 Parmentier 117154 X 2,908,571 10/1959 Roman 96--85 X 3,046,128 7/1962 Klimkowski et al. 96-75 X 3,069,268 12/1962 Herrick et al. 96--75 X 3,183,093 5/1965 Schlesinger et a1. 96-75 X OTHER REFERENCES Casey, James P.: Pulp and Paper, 2nd Ed., 3rd vol., Interscience Publishers Inc., 19 61, New York (see pp. 12881289, 1347).

NORMAN G. TORCHIN, Primary Examiner. C. L. BOWERS, IR., Assistant Examiner. 

